The present invention relates to a motorized rake assembly that, in conjunction with a bar screen located in a fluid canal or channel to catch and retain debris from the flowing fluid intermittently enters the channel to rake the screen bars and remove any trapped material. The rake contacts the trapped material and then ascends from the fluid channel to remove the material from the screen and elevate it to a discharge point. In particular, the present invention relates to such a raking apparatus which has at least an upper section and a rake section rotatably coupled to the upper section for rotatable movement from a first position spaced from the bar screen to a second position for removing debris from the bar screen. The rake section moves from the first position to the second position under the influence of a counterweight or other biasing force. A shock absorber placed between the rake section and the upper section controls the forward motion of the rake section to prevent damage to the rake apparatus from uncontrolled forward movement of the rake section from the first position to the second position.
It is necessary in many applications where a fluid or liquid such as water is confined to a channel, and which has debris in the fluid which must be periodically removed from a debris catcher such as a bar screen, to provide an automatic device for removing the debris which accumulates against the screen as necessary from time to time. These devices include some type of a rake which can be intermittently lowered into the fluid carrying channel to engage the debris retained or trapped by the bar screen and then moved upwardly out of the channel pulling the debris with the rake. When the rake has elevated the debris to the discharge point, some type of automatic device, well known in the art, scrapes the rake free of the debris and the rake may then be lowered back into the fluid where it again engages the debris retained by the bar screen to remove it from the liquid channel.
One of the problems associated with the prior art is the fact that the rake section must be forced in the direction of the bar screen with sufficient force to allow the rake teeth to penetrate the debris that is caught by the bar screen and allow it to be removed from the channel. The means of forcing the rake section in the direction of the bar screen varies but usually has some type of a counterweight which applies an extra force to the rake section in addition to the weight of the rake itself to force it in the direction of the bar screen. In addition, of course, if the rake section is moving in the direction of any fluid flow in the channel the pressure from the fluid flow in the channel also contributes to forcing the rake section towards the bar screen. Serious problems can occur when the rake section comes forward with considerable force applied to it and an impact against the bar screen can be damaging not only to the rake equipment but also to the bar screen. In addition, if an obstacle is caught in the channel between the bar screen and the approaching rake, the force of the rake striking the obstacle may also cause damage to the rake apparatus.
In the present invention, the rake assembly travels downwardly into the fluid channel along a first guide track or channel in a frame assembly, moves forward in a transition guide track to a second guide track parallel to the first and travels back up the second guide track to its initial position while raking the screen during the return travel.
The present invention reduces the falling force of the rake in its transition from the first guide track to the second guide track for engagement with the bar rake. This is accomplished with a shock absorber placed between the rake section and the upper section which not only reduces the impact force at the transition to the second guide track, but also controls the speed of transition from the first guide track to the second guide track.
More particularly, a rotary shock absorber is attached between the upper section and the midsection to control the force of counterweights attached to the midsection which force the midsection to rotate about its pivot point with the upper section where the rotary shock absorbers are located. The lower section or rake section is pivotally attached to the midsection to allow the midsection with its counterweights to carry the lower rake section forward in the direction of the bar screen.
Thus, it is an object of the present invention to reduce the impact of the rake section against either debris or the bar screen.
It is also an object of the present invention to reduce the falling force of the rake section in its transition from the first to the second guide track for engagement of the rake with the bar screen.
It is still another object of the present invention to control the speed of transition of the rake section from the first to the second guide track for engagement with either debris or the bar screen.
It is still another object of the present invention to utilize a shock absorber, and, in particular, a rotary shock absorber, between the upper section and the rake section to control the transition speed and impact of the rake section as it travels from a first position spaced from said bar screen to a second position for engagement with debris or the bar screen.